JP2014030922A - Driving device and image forming apparatus including the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a driving device capable of reliably detecting an abnormality in a pulse signal output from an encoder, and thus capable of preventing malfunction of a motor, and an image forming apparatus.SOLUTION: In a driving device 151 including a motor 101, an encoder 120, a control circuit 121, a driver circuit 125, and a reduction gear 102b that engages with a gear 102a provided in an output shaft 124 and can transmit rotation of the output shaft 124 to a driven unit, the reduction gear 102b is composed of a gear containing a one-way clutch for transmitting rotation only in a forward direction, the control circuit 121 rotates the motor 101 in a backward direction in which the reduction gear 102b is idled while performing an abnormality detection operation for detecting an abnormality in the encoder 120 on the basis of a pulse signal output from a photosensor 122 during the rotation in the backward direction, and inhibits the rotation of the motor 101 on the condition that an abnormality has been detected by the abnormality detection operation.

Description

  The present invention relates to a driving device used in an image forming apparatus such as a copying machine, a facsimile machine, a printer, or a complex machine of these.

  In general, a motor is used as a driving force source in many parts of an image forming apparatus such as a registration unit, a paper transport unit, and a reading unit.

  Conventionally, as an image forming apparatus equipped with this type of motor, a motor that rotates a photosensitive drum, a motor drive control unit that controls driving of the motor, and a motor that rotates based on a signal from the motor drive control unit There is known a motor driver including a motor driver that supplies a current for the purpose and an encoder that generates a pulse signal to grasp the rotation state of the motor (for example, see Patent Document 1). The above-mentioned encoder is attached to a rotating shaft of a motor or a portion having accuracy of rotation and moving speed, and generates a pulse output corresponding to the speed.

  In the image forming apparatus described in Patent Literature 1, motor encoder data is sampled at regular intervals, and whether or not an abnormality has occurred in the apparatus is determined based on a frequency analysis result obtained by frequency analysis of the data. It is like that.

  However, in the conventional image forming apparatus as described above, when foreign matter such as resin or solder scraps adheres to the encoder portion (for example, encoder disk or photosensor), for example, slits provided at predetermined angular intervals. There is a possibility that an accurate pulse signal cannot be generated because a part of the signal is blocked, and an incorrect pulse signal is output. In this case, in the conventional image forming apparatus, even if an attempt is made to detect the abnormality based on the frequency analysis result of the encoder data, the load fluctuations of various units such as the photosensitive drum connected to the motor via the gear are affected, As described above, there is a problem that a pulse signal output in error cannot be detected as abnormal. An abnormal pulse signal can also cause a malfunction of the motor.

  The present invention has been made to solve the above-described problems, and can reliably detect an abnormality in a pulse signal output from an encoder, thereby preventing a malfunction of a motor. It is another object of the present invention to provide an image forming apparatus.

  In order to achieve the above object, a drive device according to the present invention is an encoder comprising a motor as a drive source, an encoder disk fixed to the output shaft of the motor, and a photosensor for detecting a sensor reading unit of the encoder disk. A control means for controlling the rotation of the motor, a driver for supplying driving power to the motor based on a signal from the control means, a gear provided on the output shaft, and a rotation of the output shaft. In the drive device including a transmission gear that can be transmitted to the driven unit, the transmission gear is configured by a one-way clutched gear that transmits rotation only in the positive direction, and the control means causes the transmission gear to idle. The motor is rotated in the reverse direction, and the encoder is rotated based on a detection signal output from the encoder during the reverse rotation. Run the abnormality detecting an abnormality detecting operation of da, abnormal by the abnormality detecting operation has a structure that prohibits rotation of the motor on the condition that has been detected.

  According to the present invention, it is possible to provide a drive device and an image forming apparatus that can reliably detect an abnormality in a pulse signal output from an encoder and can prevent malfunction of a motor.

1 is a schematic configuration diagram illustrating an image forming apparatus according to an embodiment of the present invention. It is a block diagram of the process cartridge which concerns on one embodiment of this invention. 1 is a schematic configuration diagram of a document conveying device according to an embodiment of the present invention. It is the perspective view which looked at the roller drive part of the original conveying apparatus which concerns on one embodiment of this invention from one direction. It is the perspective view which looked at the roller drive part of the original conveying apparatus which concerns on one embodiment of this invention from the other direction. 1 is a schematic configuration diagram of a driving device of a document conveying device according to an embodiment of the present invention. 1 is a schematic configuration diagram of a driving device of a document conveying device according to an embodiment of the present invention. It is a block diagram which shows the structure of the drive device which concerns on one embodiment of this invention. BRIEF DESCRIPTION OF THE DRAWINGS It is an external view of the motor of the drive device which concerns on one embodiment of this invention, Comprising: (a) is the perspective view seen from one direction, (b) is the perspective view seen from the other direction. It is a perspective view of an encoder disk concerning one embodiment of the present invention, (a) shows a slot type and (b) shows a photo etching type. It is a schematic block diagram of the transmission gear which concerns on one embodiment of this invention. It is a functional block diagram of the control circuit which concerns on one embodiment of this invention. It is a processing flow of the abnormality detection operation | movement of an encoder performed with the control circuit which concerns on one embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  First, the configuration will be described.

  FIG. 1 shows a schematic configuration of an image forming apparatus according to an embodiment of the present invention.

  As shown in FIG. 1, the image forming apparatus 100 is a toner image that is a visible image of yellow, magenta, cyan, and black (hereinafter referred to as “Y”, “M”, “C”, and “K”, respectively). Are provided with four process cartridges 6Y, 6M, 6C and 6K.

  These use Y toner, M toner, C toner, and K toner of different colors as the image forming agent, but the other configurations are the same. Each of the process cartridges 6Y, 6M, 6C, and 6K can be attached to and detached from the main body of the image forming apparatus 100, and the consumable parts can be replaced at a time. Hereinafter, the process cartridge 6Y for generating a Y toner image will be described as an example.

  As shown in FIG. 2, the process cartridge 6Y includes a photosensitive drum 1Y as a latent image carrier, a drum cleaning device 2Y, a charge eliminating device (not shown), a charging device 4Y, a developing device 5Y, and the like.

  The charging device 4Y uniformly charges the surface of the photosensitive drum 1Y that is rotated clockwise in the drawing by a drum driving mechanism (not shown). The uniformly charged surface of the photosensitive drum 1Y is exposed and scanned by the laser beam L to carry a Y electrostatic latent image. The Y electrostatic latent image is developed into a Y toner image by the developing device 5Y using Y toner. Then, intermediate transfer is performed on the intermediate transfer belt 8.

  The drum cleaning device 2Y removes the toner remaining on the surface of the photosensitive drum 1Y after the intermediate transfer process. The static eliminator neutralizes residual charges on the photosensitive drum 1Y after cleaning. By this charge removal, the surface of the photosensitive drum 1Y is initialized and prepared for the next image formation.

  Similarly, in the other process cartridges 6M, 6C, and 6K, M toner images, C toner images, and K toner images are formed on the photosensitive drums 1M, 1C, and 1K, respectively. Transcribed.

  Further, as shown in FIG. 1, an exposure device 7 is disposed below each process cartridge 6Y, 6M, 6C, 6K in the drawing.

  The exposure device 7 serving as a latent image forming unit irradiates the photosensitive drums 1Y, 1M, 1C, and 1K in the process cartridges 6Y, 6M, 6C, and 6K with a laser beam L emitted based on the image information. .

  By this exposure, Y electrostatic latent images, M electrostatic latent images, C electrostatic latent images, and K electrostatic latent images are formed on the photosensitive drums 1Y, 1M, 1C, and 1K, respectively. The exposure device 7 irradiates the photosensitive drum with a laser beam L emitted from a light source through a plurality of optical lenses and mirrors while scanning with a polygon mirror rotated by a motor.

  In FIG. 1, on the lower side of the exposure apparatus 7 in the drawing, a paper supply unit having a paper storage cassette 26, a paper supply roller 27 incorporated therein, a registration roller pair 28, and the like is disposed.

  The paper storage cassette 26 stores a plurality of paper sheets 99 as recording materials, and a paper feed roller 27 is brought into contact with the uppermost paper sheet 99. When the paper feed roller 27 is rotated counterclockwise in the drawing by a drive mechanism (not shown), the uppermost paper 99 is fed toward the rollers of the registration roller pair 28.

  The registration roller pair 28 rotationally drives both rollers so as to sandwich the paper 99, but temporarily stops rotating immediately after sandwiching. Then, the sheet 99 is sent out toward a secondary transfer nip described later at an appropriate timing.

  In FIG. 1, an intermediate transfer unit 15 is disposed above the process cartridges 6Y, 6M, 6C, and 6K. The intermediate transfer unit 15 moves endlessly while the intermediate transfer belt 8 serving as an intermediate transfer member serving as a transfer material is stretched. It is installed.

  The intermediate transfer unit 15 includes a belt cleaning device 10 in addition to the intermediate transfer belt 8. Also provided are four primary transfer bias rollers 9Y, 9M, 9C, 9K, a secondary transfer backup roller 12, a cleaning backup roller 13, a tension roller 14, and the like.

  The intermediate transfer belt 8 is endlessly moved in the counterclockwise direction in the figure by the rotational drive of at least one of the rollers while being stretched around these seven rollers. The primary transfer bias rollers 9Y, 9M, 9C, and 9K respectively sandwich the intermediate transfer belt 8 that is moved endlessly in this manner between the photosensitive drums 1Y, 1M, 1C, and 1K, respectively. Is forming. In these systems, a transfer bias having a polarity opposite to that of toner (for example, plus polarity) is applied to the back surface (inner circumferential surface of the loop) of the intermediate transfer belt 8.

  All the rollers except the primary transfer bias rollers 9Y, 9M, 9C, and 9K are electrically grounded. The intermediate transfer belt 8 sequentially passes through the primary transfer nips for Y, M, C, and K along with the endless movement thereof, and the Y toner images on the photosensitive drums 1Y, 1M, 1C, and 1K. , The M toner image, the C toner image, and the K toner image are superimposed and primarily transferred. As a result, a four-color superimposed toner image (hereinafter referred to as “four-color toner image”) is formed on the intermediate transfer belt 8.

  In addition, the intermediate transfer unit 15 is in contact with or separated from the photosensitive drums 1Y, 1M, and 1C (not shown) to contact and separate the intermediate transfer belt 8 with the intermediate transfer belt 8 in contact with the photosensitive drum 1K. A mechanism is also provided.

  The secondary transfer backup roller 12 sandwiches the intermediate transfer belt 8 between the secondary transfer roller 19 and forms a secondary transfer nip. The four-color toner image formed on the intermediate transfer belt 8 is transferred to the paper 99 at the secondary transfer nip. Then, combined with the white color of the paper 99, a full color toner image is obtained.

  Untransferred toner that has not been transferred to the paper 99 adheres to the intermediate transfer belt 8 after passing through the secondary transfer nip. This is cleaned by the belt cleaning device 10. In the secondary transfer nip, the sheet 99 is sandwiched between the intermediate transfer belt 8 whose surface moves in the forward direction and the secondary transfer roller 19 and is conveyed in a direction opposite to the registration roller pair 28 side.

  The sheet 99 fed from the secondary transfer nip is affected by heat and pressure when passing between the rollers of the fixing unit 20 as a detachable unit with respect to the image forming apparatus 100 main body. The toner image is fixed. Thereafter, the sheet 99 is discharged out of the apparatus through the rollers of the pair of discharge rollers 29.

  A stack unit 30 is formed on the upper surface of the casing of the main body of the image forming apparatus 100, and the sheets 99 discharged out of the apparatus by the discharge roller pair 29 are sequentially stacked on the stack unit 30.

  A bottle support portion 31 is disposed between the intermediate transfer unit 15 and the stack portion 30 located above the intermediate transfer unit 15. In the bottle support portion 31, toner bottles 32Y, 32M, 32C, and 32K are set as agent containers for storing the respective color toners.

  Each color toner in each of the toner bottles 32Y, 32M, 32C, and 32K is appropriately supplied to the developing devices of the process cartridges 6Y, 6M, 6C, and 6K by a toner supply device (not shown). The toner bottles 32Y, 32M, 32C, and 32K are detachable from the main body of the image forming apparatus 100 independently of the process cartridges 6Y, 6M, 6C, and 6K.

  FIG. 3 is a diagram showing a configuration of the document conveying device of the image forming apparatus according to the embodiment of the present invention. This document conveying apparatus is applied to a read document processing apparatus (hereinafter referred to as ADF) that conveys an image to be read to a fixed reading device unit and reads an image while conveying the image at a predetermined speed. .

  The basic configuration, operation and action will be described below.

  The document conveying device 150 is arranged on the upper part as a part of the image forming apparatus 100 configured as a copying apparatus, an MFP, or the like. The document conveying device 150 includes a document setting unit A, a separation feeding unit B, a registration unit C, a turn unit D, a first reading and conveying unit E, a second reading and conveying unit F, and a sheet discharging unit G. And a stack portion H.

  In the document setting portion A, a read document bundle is set. The separation feeding unit B separates and feeds the originals one by one from the original bundle set in the original setting unit A. The registration unit C has a function of primary and abutting alignment of the document fed from the separation feeding unit B and a function of pulling out and transporting the document after alignment. The turn part D turns the original conveyed from the resist part C and conveys the original surface toward the reading side (downward). The first reading conveyance unit E reads the surface image of the document from below the contact glass. The second reading conveyance unit F reads the back side image of the document after being read by the first reading conveyance unit E. The paper discharge unit G discharges the original whose front and back have been read out of the apparatus. The stack unit H stacks and holds documents after reading.

  Although not shown, the document conveying device 150 is a drive unit that drives these conveying operations, such as a pickup motor, a sheet feeding motor, a reading motor, a sheet discharging motor, a bottom plate raising motor, and an ADF that controls a series of operations. A control unit is provided.

  The document table 42 includes a movable document table 43, on which a sheet 99 to be read is set. The sheet 99 is set on the document table 42 with the document surface facing upward. The document table 42 is provided with a side guide (not shown), and is positioned in a direction perpendicular to the conveyance direction of the paper 99.

  The set paper 99 is detected by the set filler 44 and the set sensor 45, and the detection information is transmitted to the main body control unit.

  Further, document length detection sensors 70 and 71 (a reflection type sensor or an actuator type sensor that can detect even 99 sheets of paper) are arranged on the document table 42. Document length detection sensors 70 and 71 determine the length of the document in the conveyance direction. At this time, the document length detection sensors 70 and 71 are arranged so as to be able to determine at least whether the document size is vertical or horizontal.

  The movable document table 43 can be moved up and down in the directions of arrows a and b by a bottom plate raising motor. When the set filler 44 and the set sensor 45 detect that the original is set on the movable original table 43, the bottom plate raising motor is rotated forward so that the uppermost surface of the original bundle comes into contact with the pickup roller 47. Raise.

  The pickup roller 47 is operated by a pickup motor in the directions of arrows c and d by a cam mechanism, and the movable document table 43 is raised and pushed by the upper surface of the document on the movable document table 43 to rise in the c direction, and a table elevation detection sensor 48. The upper limit can be detected.

  When the print key of the main body operation unit is pressed and a document feed signal is transmitted from the main body control unit to the ADF control unit via the I / F, the roller of the pickup roller 47 is rotated by the normal rotation of the paper feed motor. Then, several (ideally one) originals on the original table 42 are picked up. The rotation direction is a direction in which the uppermost document is conveyed to the sheet feeding port.

  The paper feed belt 49 is driven in the paper feed direction by the forward rotation of the paper feed motor, and the reverse roller 50 is driven to rotate in the reverse direction to the paper feed by the forward rotation of the paper feed motor, and the uppermost document and the lower side thereof. The document is separated, and only the uppermost document can be fed.

  That is, the reverse roller 50 is brought into contact with the paper feed belt 49 at a predetermined pressure, and when the paper is in direct contact with the paper feed belt 49 or through a sheet of paper, the reverse roller 50 is driven by the rotation of the paper feed belt 49. It is designed to rotate counterclockwise. The reverse roller 50 is set so that the follower force is lower than the torque of the torque limiter when two or more originals enter between the paper feed belt 49 and the reverse roller 50. Accordingly, the reverse roller 50 rotates in the clockwise direction, which is the original driving direction, and functions to push back the excess original. Thereby, double feeding is prevented.

  The original document separated into one sheet by the action of the paper feed belt 49 and the reverse roller 50 is further fed by the paper feed belt 49, and its leading edge is detected by the abutment sensor 51. Thereafter, the document whose leading edge is detected hits the pull-out roller 52 which has further stopped and stopped. The document after the abutting is then fed by a predetermined distance from the detection of the abutting sensor 51, and as a result, is pressed against the pull-out roller 52 with a certain amount of deflection. By stopping the paper feed motor in a state where the original is pressed against the pull-out roller 52 with a predetermined amount of deflection, the drive of the paper feed belt 49 is stopped.

  At this time, the pickup motor 47 is retracted from the upper surface of the document by rotating the pickup motor, and the document is fed only by the conveying force of the paper feed belt 49, so that the leading edge of the document enters the nip of the upper and lower rollers of the pull-out roller 52. Then, tip alignment (skew correction) is performed.

  The pull-out roller 52 has the skew correction function and conveys the skew-corrected document after separation to the intermediate roller 54, and is driven by the reverse rotation of the paper feed motor. Note that the pull-out roller 52 and the intermediate roller 54 are driven at the time of reverse rotation of the paper feed motor, but the pickup roller 47 and the paper feed belt 49 are not driven.

  A plurality of document width sensors 53 are arranged in the depth direction and detect the size in the width direction perpendicular to the transport direction of the document transported by the pull-out roller 52. Further, the length of the document in the conveyance direction is detected from the motor pulse by reading the leading edge and the trailing edge of the document with the butting sensor 51.

  When the document is transported from the resist section C to the turn section D by driving the pull-out roller 52 and the intermediate roller 54, the transport speed at the resist section C is set to be higher than the transport speed at the first reading transport section E. Thus, the processing time for sending the document to the reading unit is shortened.

  When the leading edge of the document is detected by the reading entrance sensor 55, when the leading edge of the document enters the nip between the upper and lower roller pairs of the reading entrance roller 56, deceleration is started in order to make the document transportation speed the same as the reading transportation speed. At the same time, the reading motor is driven to rotate forward to drive the reading inlet roller 56, the reading outlet roller 63, and the CIS outlet roller 67.

  When the leading edge of the document is detected by the registration sensor 57, the document sensor decelerates over a predetermined conveyance distance, pauses just before the reading position 60 where the first reading unit (not shown) is arranged, A registration stop signal is transmitted via / F.

  Subsequently, when a reading start signal is received from the main body control unit, the document whose registration has been stopped is transported at an increased speed so as to rise to a predetermined transport speed until the leading end of the document reaches the scanning position.

  At the timing when the leading edge of the document detected by the pulse count of the reading motor reaches the reading section, a gate signal indicating the effective image area in the sub-scanning direction on the first surface is sent to the main body control section, and the first reading section is moved to the trailing edge of the document. Sent until is removed.

  In the case of reading a single-sided original, the original that has passed through the first reading conveyance unit E is conveyed to the paper discharge unit G through the second reading unit 65. At this time, when the leading edge of the document is detected by the paper discharge sensor 64, the paper discharge motor is driven to rotate forward to rotate the paper discharge roller 68 counterclockwise.

  Further, the discharge motor drive speed is reduced immediately before the trailing edge of the document comes out of the nip between the upper and lower roller pairs of the discharge roller 68 by the discharge motor pulse count from the detection of the leading edge of the document by the discharge sensor 64 to discharge the sheet. Control is performed so that the document discharged onto the tray 69 does not jump out.

  In the case of double-sided document reading, the second reading configured by the CCD line sensor is performed at the timing when the leading edge of the document reaches the second reading unit 65 by the pulse count of the reading motor after the discharge sensor 64 detects the leading edge of the document. A gate signal indicating an effective image area in the sub-scanning direction is transmitted from the ADF control unit to the unit 65 through the reading unit until the trailing edge of the document passes.

  The surface of the second reading unit 65 is provided with a coating member that has been subjected to a coating process in order to prevent vertical streaks due to transfer of glue on the original onto the reading line.

  This coating member is formed by applying a coating material having a dirt decomposition function or a hydrophilic coating material to the reading surface of the second reading unit 65. These coating materials can use a well-known thing.

  4 and 5 are diagrams showing a schematic configuration of a roller driving unit of the document conveying device of the image forming apparatus according to the embodiment of the present invention.

  4 and 5, the driving device 151 includes a motor for driving any one of the driving rollers of the document conveying device 150 shown in FIG. 3, a control circuit for the motor, and the like.

  In the driving device 151, the motor 101 as a driving source is configured as an inner rotor type DC brushless motor, and a roller is provided via a gear 102 a and reduction gears 102 b, 102 c, 102 d, 102 e, 102 f fixed to the output shaft 124. 104 is rotated. The motor 101 is not limited to the inner rotor type DC brushless motor, and various motors such as an outer rotor type, a brushed DC motor, or a stepping motor can be used.

  The roller 104 is, for example, the reading entrance roller 56, the reading exit roller 63, or the CIS exit roller 67 of the document conveying device 150 in FIG. The roller 104 may be, for example, the paper feed roller 27 of the main body of the image forming apparatus 100 in FIG.

  The drive device 151 includes an encoder 120 including a photo sensor 122 and an encoder disk 123.

  The encoder disk 123 has a predetermined number of slits at predetermined angular intervals in the circumferential direction, is fixed perpendicularly and concentrically to the output shaft 124, and rotates with the rotation of the output shaft 124.

  The photo sensor 122, which is an optical sensor, is attached to the motor 101 with the encoder disk 123 sandwiched between them, and the optical path is transmitted and blocked by the slits of the encoder disk 123, and the pulse signal is transmitted to the control circuit 121. Yes. Therefore, a portion where the slit of the encoder disk 123 is formed is a sensor reading unit detected by the photosensor 122.

  The control circuit 121 measures the pulse signal from the photosensor 122 to derive the rotation amount and rotation speed of the motor 101 and obtains the position and speed information of the paper 99 from the position and speed information of the roller 104. It becomes possible.

  Note that the photosensor 122 includes two sets of light-emitting elements and light-receiving elements, and is arranged so that the phase difference between the pulse signals is a predetermined amount (π / 2 [rad] in this embodiment). .

  The control circuit 121 generates an operation signal of the motor 101 based on a signal from a target drive signal generation device (not shown) and the photosensor 122, sends the operation signal to the driver circuit 125, and then converts the operation signal from the driver circuit 125 to the operation signal. The roller 104 is driven by passing the combined current to the motor 101.

  FIG. 6 is a diagram showing a schematic configuration of a driving device of the document conveying device of the image forming apparatus according to the embodiment of the present invention.

  In FIG. 6, a driving device 151 includes a motor that drives any one of the driving rollers of the document conveying device 150 shown in FIG. 3, a control circuit thereof, and the like. Here, an example in which the roller pair 103a, 103b is applied as a driven unit of the driving device 151 instead of the roller 104 described above will be described.

  In the driving device 151, the sheet 99 (see FIG. 3) is conveyed while being sandwiched between the roller pairs 103a and 103b. The roller pair 103a, 103b is, for example, the reading entrance roller 56, the reading exit roller 63, or the CIS exit roller 67 of the document conveying device 150 in FIG. The roller pairs 103a and 103b may be, for example, the paper feed roller 27 of the image forming apparatus 100 main body in FIG.

  The motor 101 rotates the roller pair 103a and 103b through a gear 102a and reduction gears 102b, 102c, 102d, and 102e fixed to the output shaft 124.

  The encoder disk 123 has a predetermined number of slits at predetermined angular intervals in the circumferential direction, is fixed perpendicularly and concentrically to the output shaft 124, and rotates with the rotation of the output shaft 124.

  A photo sensor 122, which is an optical sensor, is attached to the motor 101 with an encoder disk 123 sandwiched between them. The optical path is transmitted and blocked by a slit of the encoder disk 123, and is controlled as a pulse signal by a light receiving element of the photo sensor 122. Is transmitted to the circuit 121.

  By measuring this pulse signal, the control circuit 121 can derive the rotation amount and rotation speed of the motor 101 and obtain the position and speed information of the paper 99 from the position and speed information of the roller pairs 103a and 103b. It becomes.

  Note that the photosensor 122 includes two sets of light-emitting elements and light-receiving elements, and is arranged so that each pulse signal phase difference is a predetermined amount (π / 2 [rad] in this embodiment).

  The control circuit 121 generates an operation signal of the motor 101 based on a signal from a target drive signal generation device (not shown) and the photosensor 122, sends the operation signal to the driver circuit 125, and then converts the operation signal from the driver circuit 125 to the operation signal. By passing the combined current to the motor 101, the roller pairs 103a and 103b are driven.

  FIG. 7 is a diagram showing a schematic configuration of the driving device of the document conveying device of the image forming apparatus according to the embodiment of the present invention.

  In FIG. 7, a driving device 151 includes a motor that drives any one of the driving rollers of the document conveying device 150 shown in FIG. 3, a control circuit thereof, and the like. Here, an example in which a coupling 126 is added to the driving device 151 will be described.

  In the driving device 151, the sheet 99 (see FIG. 3) is conveyed while being sandwiched between the roller pairs 103a and 103b. The roller pair 103a, 103b is, for example, the reading entrance roller 56, the reading exit roller 63, or the CIS exit roller 67 of the document conveying device 150 in FIG. The roller pairs 103a and 103b may be, for example, the paper feed roller 27 of the image forming apparatus 100 main body in FIG.

  The motor 101 rotates the roller pair 103a and 103b through a gear 102a and reduction gears 102b, 102c, 102d, and 102e fixed to the output shaft 124.

  The encoder disk 123 has a predetermined number of slits at predetermined angular intervals in the circumferential direction, and is fixed perpendicularly and concentrically to the axis of the motor 101 via the output shaft 124 and the coupling 126. It rotates with the rotation of 124.

  The photo sensor 122, which is an optical sensor, is attached to a fixing member (not shown) so as to sandwich the encoder disk 123. Light is reflected at a portion of the encoder disk 123 where there is no slit, and light is received by the light receiving element of the photo sensor 122. A pulse signal is generated based on the presence or absence of this detection, and this pulse signal is transmitted to the control circuit 121.

  By measuring this pulse signal, the control circuit 121 can derive the rotation amount and rotation speed of the motor 101 and obtain the position and speed information of the paper 99 from the position and speed information of the roller pairs 103a and 103b. It becomes.

  Note that the photosensor 122 includes two sets of light-emitting elements and light-receiving elements, and is arranged so that each pulse signal phase difference is a predetermined amount (π / 2 [rad] in this embodiment).

  The control circuit 121 generates an operation signal of the motor 101 based on a signal from a target drive signal generation device (not shown) and the photosensor 122, and sends the operation signal to the driver circuit 125. Thereafter, the driver circuit 125 By causing a current corresponding to the operation signal from 121 to flow through the motor 101, the roller pairs 103a and 103b are driven.

  FIG. 8 is a diagram showing the configuration of the drive device of the image forming apparatus according to the embodiment of the present invention.

  In FIG. 8, a driving device 151 includes a motor that drives any one of the driving rollers of the image forming apparatus 100 shown in FIG. 1 or the document conveying device 150 shown in FIG.

  In the driving device 151, a rotation direction signal and a moving pulse number signal are passed from an external target drive signal generation means 130 to a target position / speed calculation circuit 131 in the control circuit 121. That is, the target position / velocity calculation circuit 131 in the control circuit 121 obtains a rotation direction signal and a signal of the number of movement pulses as the target drive signal from the external target drive signal generation means 130.

  The target position / speed calculation circuit 131 derives the target position and the target speed from the obtained information and time information of an oscillator (not shown), and transmits a signal to the position / speed tracking controller 133.

  In addition, the motor position / speed calculation circuit 132 in the control circuit 121 measures the pulses of the encoder disk 123 by the photo sensor 122 configured as a two-channel photo sensor. The photo sensor 122 and the encoder disk 123 are configured as a two-channel rotary encoder.

  In the present embodiment, the number of pulses per revolution of the encoder disk 123 is 100 pulses. The number of pulses per revolution of the encoder disk 123 is preferably 200 pulses or less in order to detect the rotation of the output shaft 124 of the motor 101 at a low cost.

  Also, the number of pulses per revolution of the encoder disk 123 is set to 12 × N pulses (N is a natural number) or 50 × N pulses in order to facilitate replacement of the stepping motor with the inner rotor type DC brushless motor. Is preferred.

  Here, the photosensor 122 configured as a two-channel photosensor has two sets of light-emitting elements and light-receiving elements, and each pulse signal phase difference is a predetermined amount (in this embodiment, π / 2 [rad]). It is arranged to become. Therefore, the motor position / speed calculation circuit 132 can know the rotation direction using the phase difference.

  The motor position / speed calculation circuit 132 derives the motor position and motor speed from the obtained information and time information of an oscillator (not shown), and transmits a signal to the position / speed tracking controller 133.

  The position / speed tracking controller 133 performs control so that the target position matches the motor position, and the target speed matches the motor speed, and outputs signals such as PWM output, rotation direction, start / stop, and brake as necessary. The signal is sent to the circuit 125.

  The driver circuit 125 is configured as a four-quadrant driver, and controls the motor current and the PWM voltage from the signal obtained from the position / speed tracking controller 133 and the Hall signal from the Hall IC 135.

  That is, in the driving device 151, the control circuit 121 obtains the target rotation amount ΔXt and the target total rotation amount Xt per unit time from the target drive signal, and per unit time from the output signals from the photosensor 122 and the encoder disk 123. Motor rotation amount ΔXm and motor total rotation amount Xm are obtained, and thereafter, target total rotation amount Xt and motor total rotation amount Xm are equal, and target rotation amount ΔXt per unit time and motor rotation amount ΔXm per unit time are equal. Thus, the rotational speed of the motor 101 is controlled by changing the signal to the driver circuit 125.

  In the present embodiment, the driver circuit 125 is shown in a form that is not mounted on the motor 101. However, when the driver circuit 125 is mounted on a board on the motor 101, the number of harnesses can be reduced, thereby reducing the cost. Connected.

  In the present embodiment, the target drive signal generation unit 130 is not included in the drive device 151 and is provided in a main body control unit (not shown) of the image forming apparatus 100, an ADF control unit (not shown) of the document conveyance device 150, or the like. However, the target drive signal generation means 130 may be included in the drive device 151.

  FIG. 9A and FIG. 9B are perspective views showing the configuration of the motor of the image forming apparatus according to the embodiment of the present invention.

  As shown in FIGS. 9A and 9B, the gear 102a is directly geared to the output shaft 124 of the motor 101, whereby the reduction ratio of the first stage of the motor can be increased and the cost can be reduced. It is like that.

  An encoder disk 123 is coaxially fixed to the end of the output shaft 124 on the side opposite to the gear 102a which is a drive transmission portion. The photosensor 122 is attached to the motor 101, and the driver circuit 125 (see FIG. 8) is also attached to the substrate on the motor 101. A connector 127 is attached to the board on the motor 101 so that motor signals and encoder signals can be input and output.

  In addition, since a ball bearing is used for the bearing portion of the motor 101, the frictional force is reduced as compared with the case where a sintered bearing or the like is used. Therefore, by using the motor 101 which is a DC motor. The efficiency can be further increased and the durability can be increased.

  FIGS. 10A and 10B are perspective views showing the configuration of the encoder disk of the image forming apparatus according to the embodiment of the present invention.

  FIG. 10A shows the encoder disk 123 as a slot type. In FIG. 10A, the encoder disk 123 is constituted by a metal plate having slit-shaped holes 123a formed at equal intervals in the circumferential direction (rotation direction) by etching or the like. By having a slit shape, the light receiving element of the photosensor 122 detects the presence or absence of a signal based on the presence or absence of the slit-shaped hole, and detects the pulse.

  FIG. 10B shows the encoder disk 123 as a photo-etching type. In FIG. 10B, the encoder disk 123 is formed by printing a slit 123b with black ink on a film. Depending on the presence or absence of this black ink, the light receiving element of the photosensor 122 indicates the presence or absence of a signal or the amount of light. Differences are detected and pulse detection is performed. In the encoder disk 123 shown in FIG. 10B, black ink is used. However, as long as a difference in light quantity (including presence / absence) can be detected, the ink may not be black ink.

  FIG. 11 is a schematic cross-sectional view of the transmission gear of the drive device according to the embodiment of the present invention.

  As shown in FIG. 11, a reduction gear 102b as a transmission gear meshes with a gear 102a provided on an output shaft 124 of the motor 101, and rotation of the output shaft 124 is, for example, a roller 104 as a driven unit (see FIG. 4). And a pair of rollers 103a and 103b (see FIG. 6).

  The reduction gear 102b is constituted by a one-way clutch-equipped gear incorporating a one-way clutch 105 that transmits rotation only in the positive direction. As the one-way clutch 105, for example, a known one-way clutch such as a sprag type or a cam type can be used.

  Next, the abnormality detection operation of the encoder 120 will be described with reference to FIGS.

  First, the configuration for executing the abnormality detection operation of the encoder 120 will be described with reference to FIG.

  As shown in FIG. 12, the control circuit 121 rotates the motor 101 in the reverse direction in which the reduction gear 102 b idles, that is, the rotation direction in which the rotation of the output shaft 124 is not transmitted to the driven unit as the abnormality detection operation is performed. It is like that.

  The control circuit 121 detects an abnormality of the encoder 120 based on the detection signal (pulse signal) output from the photosensor 122 when the motor 101 rotates in the reverse direction as described above. .

  Specifically, the control circuit 121 includes an FFT analysis unit 160 and an abnormality detection unit 161 for performing an abnormality detection operation.

  The FFT analysis unit 160 acquires a detection signal (pulse signal) output from the photosensor 122 when the motor 101 rotates in the reverse direction, and performs FFT analysis (fast Fourier transform) on the detection signal to perform frequency analysis. Yes. Further, the FFT analysis unit 160 removes frequency components for one rotation period of the reduction gear 102b when performing frequency analysis. That is, when FFT conversion is performed, a frequency component corresponding to the rotational speed of the motor 101 and a frequency component resulting from the meshing frequency component of the reduction gear 102b, the eccentricity of the rotating shaft, and the like are obtained simultaneously. For this reason, the FFT analysis unit 160 removes unnecessary meshing frequency components of the reduction gear 102b, resulting frequency components, and the like in order to extract only the frequency components of the motor 101 used in the abnormality detection unit 161 described later. Yes.

  The abnormality detection unit 161 detects an abnormality of the encoder 120 by comparing the peak value of the frequency (encoder pulse frequency peak value) obtained as a result of the frequency analysis by the FFT analysis unit 160 with a predetermined threshold value. It is like that. Specifically, the abnormality detection unit 161 detects an abnormality of the encoder 120 when the encoder pulse frequency peak value is larger than a predetermined threshold value. Here, the above-mentioned predetermined threshold value is an encoder pulse frequency peak value during normal rotation when no foreign matter is stuck on the encoder disk 123 or the photosensor 122, and is experimentally obtained in advance and stored in a ROM or the like. Yes.

  The control circuit 121 prohibits the rotation of the motor 101 when an abnormality of the encoder 120 is detected by the above-described abnormality detection operation. Thereby, malfunction of the motor 101 after abnormality detection is prevented.

  Further, the control circuit 121 displays an error via the operation display unit 162 at the same time as the rotation of the motor 101 is prohibited. Thereby, it is possible to notify the user of the occurrence of an abnormality in the encoder 120. Note that a warning sound may be generated instead of the error display or simultaneously with the error display. The operation display unit 162 is disposed, for example, at the upper front of the image forming apparatus 100 main body. The operation display unit 162 according to the present embodiment constitutes display means according to the present invention.

  Next, the flow of processing of the abnormality detection operation executed by the control circuit 121 will be described with reference to FIG. Such an abnormality detection operation is executed, for example, when the image forming apparatus 100 is activated (warm-up) or in a standby state where no image forming process is executed.

  As shown in FIG. 13, the control circuit 121 first rotates the motor 101 in the reverse direction in which the reduction gear 102b idles, that is, reversely rotates (step S1).

  Next, the control circuit 121 acquires a detection signal (pulse signal) output from the photosensor 122 when the motor 101 rotates in the reverse direction (step S2).

  Thereafter, the control circuit 121 performs FFT analysis on the obtained pulse signal to perform frequency analysis (step S3). Then, the control circuit 121 removes a frequency component for one rotation period of the reduction gear 102b from the plurality of frequency components obtained by frequency analysis (step S4).

  Next, the control circuit 121 determines whether or not the encoder pulse frequency peak value obtained as a result of the frequency analysis is equal to or less than a predetermined threshold value (step S5). In this determination, if the control circuit 121 determines that the encoder pulse frequency peak value is equal to or less than the predetermined threshold value, the control circuit 121 stops driving the motor 101 that has been reversely rotated in step S1, that is, reverses the motor 101. It stops (step S6) and this process is complete | finished.

  On the other hand, when the encoder pulse frequency peak value is larger than the predetermined threshold value, the control circuit 121 determines that the encoder 120 is abnormal and stops the reverse rotation of the motor 101 (step S7). Rotation of 101 is prohibited, that is, motor drive prohibition processing is performed (step S8). As a result, malfunction of the motor 101 is prevented after the abnormality of the encoder 120 is detected.

  Next, the control circuit 121 displays an error message on the operation display unit 162 (step S9), and ends this process. The display of the error message is preferably performed simultaneously with the motor drive prohibition process in step S8.

  As described above, the driving device 151 according to the present embodiment rotates the motor 101 reversely in the abnormality detection operation of the encoder 120, and based on the detection signal (pulse signal) output from the photosensor 122 during the reverse rotation. An abnormality of the encoder 120 is detected. Therefore, since the influence of the load fluctuation of the driven unit can be eliminated by the reverse rotation of the motor 101, the abnormality of the pulse signal output from the photosensor 122 (abnormality of the encoder 120) can be reliably detected without the influence of the load fluctuation. can do.

  In addition, the driving device 151 according to the present embodiment prohibits the motor 101 from rotating after the abnormality of the encoder 120 is detected, so that the malfunction of the motor 101 can be prevented.

  In addition, when an abnormality of encoder 120 is detected in the abnormality detection operation, drive device 151 according to the present embodiment displays an error message via operation display unit 162, so that an abnormality of encoder 120 occurs to the user. Can be notified. Thereby, the user can cope with the abnormality of the encoder 120 at an early stage.

100 image forming apparatus 101 motor 102a gear 102b reduction gear (transmission gear)
103a, 103b Roller pair (driven unit)
104 Roller (driven unit)
105 One-way clutch 120 Encoder 121 Control circuit (control means)
122 Photosensor 123 Encoder disk 123a Hole 123b Slit 124 Output shaft 125 Driver circuit (driver)
126 Coupling 127 Connector 150 Document Conveying Device 151 Drive Device 160 FFT Analysis Unit 161 Abnormality Detection Unit 162 Operation Display Unit (Display Unit)

JP 2010-216832 A

Claims (5)

A motor as a drive source;
An encoder disk composed of an encoder disk fixed to the output shaft of the motor and a photosensor for detecting a sensor reading unit of the encoder disk;
Control means for controlling rotation of the motor;
A driver for supplying driving power to the motor based on a signal from the control means;
In a driving device that includes a transmission gear that meshes with a gear provided on the output shaft and that can transmit the rotation of the output shaft to a driven unit.
The transmission gear is composed of a one-way clutched gear that transmits rotation only in the positive direction,
The control means rotates the motor in a reverse direction in which the transmission gear rotates idly and executes an abnormality detection operation for detecting an abnormality in the encoder based on a detection signal output from the encoder during the reverse rotation. A drive device that prohibits rotation of the motor on condition that an abnormality is detected by an abnormality detection operation.   The control means performs FFT analysis on the detection signal output from the encoder in the abnormality detection operation, performs frequency analysis, and compares the peak value obtained from the frequency analysis with a predetermined threshold value. The drive device according to claim 1, wherein an abnormality of the encoder is detected.   3. The driving apparatus according to claim 2, wherein the control unit removes a frequency component corresponding to one rotation period of the transmission gear when performing the frequency analysis. 4.   The drive device according to any one of claims 1 to 3, further comprising display means for displaying an error on condition that an abnormality is detected by the abnormality detection operation.   An image forming apparatus comprising the driving device according to claim 1.

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